Effect of intracellular iron loading on lipid peroxidation of brain slices

The effect of artificially elevated cell iron content on oxygen-derived free radical production was assessed in brain slices by use of an iron ligand, 8-hydroxyquinoline (HQ). The iron complex Fe(3+)-HQ exhibited a high lipid solubility evidenced by n-octanol/water partition coefficient and was avidely taken up by brain slices. The catalytically active form of Fe3+ within the complex was evidenced by measuring the rate of ascorbate oxidation. Lipid peroxidation was assessed by measuring the thiobarbituric acid-reactive substances (TBARS) in brain homogenates or slices exposed to two doses of Fe(3+)-HQ (10 microM/20 microM, 100 microM/200 microM) or Fe(3+)-citrate (10 microM, 100 microM). Addition of the iron complexes to homogenates or slices resulted in a dose-dependent increase in lipid peroxidation. In homogenates, the effects were grossly similar with both complexes, whereas in slices the effects of Fe-HQ were significantly higher than those of Fe-citrate. Lipid peroxidation persisted in washed slices preexposed to Fe-HQ, but not in slices preexposed to the hydrophilic iron complex Fe-citrate. Fe-HQ-induced lipid peroxidation in slices was enhanced in the presence of H2O2, an effect that was not seen using Fe-citrate. Addition of Fe-HQ to brain homogenates in the presence of salicylic acid resulted in the production of 2,3-dihydroxybenzoic acid and the effect was potentiated in the presence of H2O2. This model of iron cell loading may be useful for evaluating the efficacy of antioxidant drugs.